Food additives commonly used to thicken and stabilize processed foods disrupt the intestinal microbiota to cause inflammation, researchers found in a study of mice.

Emulsifiers are added to foods to hold together mixtures of fat and water, which would otherwise separate. Healthy mice fed a diet containing commonly used emulsifiers (1% carboxymethylcellulose or 1% polysorbate-80) developed low-grade inflammation, obesity, and metabolic syndrome, Benoit Chassaing et al reported in the February 25 issue of Nature. Furthermore, addition of the emulsifiers increased the frequency and severity of colitis that develops in IL10-null mice, which are predisposed to intestinal inflammation.

It appears that these emulsifiers perturb interaction between microbes and the intestinal epithelium, resulting in low-grade inflammation, adiposity, and its associated metabolic effects. Chassaing et al conclude that broad use of emulsifying agents might contribute to the increasing incidence of obesity, metabolic syndrome, and chronic inflammatory diseases.

Live Science explained that emulsifying agents are used thicken foods. For instance, emulsifiers help make ice cream stay creamy even after several cycles of freezing and thawing. The agents are also added to salad dressing, mayonnaise, pasta sauce, bread and cookies, wrote ScienceNews.

Nature News wrote that about 15 different emulsifiers are commonly used in processed Western foods. Regulatory agencies such as the US Food and Drug Administration says that emulsifiers are “generally regarded as safe” because there is no evidence that they increase the risk of cancer or have toxic effects in mammals.

Past studies in mice have shown that carboxymethylcellulose changed the composition of the bacterial communities that line the gut. Processed foods typically contain about 1% emulsifiers.

Chassaing et al found that healthy mice fed diets containing either emulsifier for 12 weeks began eating more and gaining weight, and had problems controlling blood sugar, compared with control mice. They found that the intestines of the mice had low-grade inflammation and less microbial diversity, and contained inflammation-associated microbes.

However, mice without intestinal bacteria did not develop inflammation or become obese after receiving the chemicals. Transplantation of intestinal microbiota from mice that developed the emulsifier-induced disorders into the microbe-free mice led to low-grade inflammation and metabolic syndrome.

The Los Angeles Times wrote that the detergent-like molecules were found to erode the mucous membrane that lines the gut and provides a buffer between the epithelial cells of the intestinal surface and the microorganisms that flourish there.

Andrew Gewirtz, the senior author of the study, told ScienceNews that emulsifiers appear to make the mucus layer more permeable, allowing certain bacteria to penetrate and cause inflammation. Bacterial infiltration of the intestinal mucosa has been associated with inflammatory disorders such as Crohn’s disease and metabolic syndrome.

“Emulsifiers are a plausible candidate to have promoted the increase in these inflammatory diseases. They are there at the scene of the crime,” said Gewirtz, who hopes to perform a study in humans and is collecting biopsies from surgery patients.

LiveScience wrote that the ideal experiment would be to compare people who are eating foods with and without these agents, but completely eliminating these compounds from the diet is a challenge. “People who want to avoid these food additives should eat more whole foods and fresh foods. Packaged products are loaded with emulsifiers and freshly cooked foods are not, so this is one of the simplest ways to avoid these agents,” Chassaing told Live Science.

Gewirtz told Nature News that previous studies may have missed the link between emulsifiers and inflammatory bowel diseases because food additives are tested in large populations. So, it is hard to detect subtle effects in people with genetic or microbial features that predispose them to these diseases.

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About the Author

Dr. Kristine Novak is the science editor for Gastroenterology and Clinical Gastroenterology and Hepatology. She has worked as an editor at biomedical research journals and as a science writer for 15 years, covering advances in gastroenterology, hepatology, cancer, immunology, biotechnology, molecular genetics, and clinical trials. She has a PhD in cell biology and an interest in all areas of medical research.